Innovative Hydrophilic Microporous Layers for Cathode Gas Diffusion Media

Abstract

In a departure from the conventional design of hydrophobic microporous layers (MPLs), the author conceived the idea of hydrophilic double MPLs. The hydrophilic layers are composed of carbon fibers and a hydrophilic polymer. The ratio of hydrophilic polymer to carbon fiber is designed to be low in the first layer (catalyst side) and high in the second layer (gas diffusion media, or GDM, side) in order that the two layers should function differently. The first layer removes liquid water from the cathode catalyst layer and the second layer retains water, thus preventing the membrane from drying-out. The membrane-electrode assembly (MEA), which uses a cathode GDM with hydrophilic double MPLs, exhibits excellent performance under both high and low humidity conditions. It was also shown that even the hydrophobic treatment of the cathode GDM substrate is not so critical when the hydrophilic double MPLs are employed. This work clearly indicates that costly hydrophobic GDM substrates and MPLs are not always necessary in the design of MEAs.